func insertionSort(arr []int) []int {
	for i := range arr {
			preIndex := i - 1
			current := arr[i]
			for preIndex >= 0 && arr[preIndex] > current {
					arr[preIndex+1] = arr[preIndex]
					preIndex -= 1
			}
			arr[preIndex+1] = current
	}
	return arr
}